In recent years, lipstick has gone beyond the point of serving the sole function of coloring the lips. Consumers are no longer satisfied with a product which serves a simple cosmetic purpose; rather, the demand is now for a product which, in addition to providing an attractive appearance, goes on smoothly, lasts all day, and also moisturizes and improves the condition of the lips. The goals of moisturizing and conditioning have proven particularly difficult when using standard lipstick formulations.
Traditional lipsticks have primarily been anhydrous, i.e., they have been composed principally of hydrophobic waxes and oils. Such products have relied on the formation of a thick occlusive film on the lips to prevent moisture loss. While to a large extent very effective in preventing water loss, such anhydrous systems are unable to achieve the more desirable end of actively reconstituting the lips' lipid barrier or attracting and binding water to the lip surface. This is largely because the low polarity and high viscosity which characterize the typical waxy components, act as a barrier to active product diffusion. Moreover, these viscous materials frequently result in a product that leaves an undesirable greasy or waxy feeling on the lips.
Notwithstanding the problems which arise with their use, the hydrophobic waxes and oils are an essential part of virtually any lipstick, in that they confer the solid physical structure required for ease of application. It has been recognized that the availability of a water-containing lip product would obviate many of the problems associated with the anhydrous systems. For example, many of the therapeutic or conditioning actives which would be useful in barrier repair or moisture attraction are water soluble. Ideally, the use of a water-in-oil emulsion system would provide the combination of features which would both confer both occlusive film-forming properties and structural integrity to the stick while still permitting delivery of the water soluble and/or water attracting actives to the lips. Nonetheless, the cosmetics industry has, to date, produced few such systems. In part, the difficulty arises in the inherent incompatibility of water with the low polarity waxes and oils; however, there are also serious problems with loss of water from the stick during storage, and the lack of stability of the water soluble actives in such a system. Generally speaking, the available systems rely entirely on the use of emulsifiers (see e.g., U.S. Pat. No. 5,342,134) to stabilize the contained actives. Since the trend in cosmetics is away from the use of emulsifiers, however, it would be preferable to design a water-in-oil emulsion system which does not rely solely on standard emulsifiers for stability of actives contained therein.
Therefore, there continues to be a need for a water-containing lip product which can moisturize and protect the lips, deliver stable water soluble actives without the use of large amounts of standard emulsifiers or surfactants, and which is not susceptible to rapid loss of water from the mass. The present invention provides such a product, and solves many of the problems encountered with other water-containing lip products.